Unsaturated polyesters

ABSTRACT

Unsaturated linear polymers have repeating units of a reaction product of a first monomer, a second monomer, a third monomer and optionally a fourth monomer. The linear polymers have a glass transition temperature ranging from about 52° C. to about 61° C. The first monomer should have a weight average molecular weight less than 200. The second monomer may be a dicarboxylic acid or diester which is different than the third monomer. A concentration of second residues of the polymer, derived from the second monomer, ranges from about 3 wt. % to about 15 wt. %, based on the total weight of the polymer. The third monomer is an aromatic dicarboxylic acid or an ester thereof. In the polymer, a concentration of third residues, derived from the third monomer, ranges from about 40 wt. % to about 55 wt. %, based on the total weight of the polymer. The fourth monomer is a diol having a higher molecular weight than the first monomer. In a process for preparing the inventive polymer, the first, second, third monomer (and optionally a fourth monomer) and/or a catalyst undergo transesterification to form the unsaturated, linear polymer.

This is a division of application Ser. No. 08/159,176 filed Nov. 30,1993, now U.S. Pat. No. 5,407,772.

BACKGROUND OF THE INVENTION

The invention is directed to unsaturated polyester polymers,particularly useful for preparing low-fix temperature, cross-linkedtoner resins. Toners made from cross-linked resins comprising theinventive unsaturated polyester polymers exhibit desirable lowtemperature fixing characteristics and offset properties.

BACKGROUND

Conventional electrophotographic processes require temperatures of160°-200° C. to fix toner on a support medium, e.g., a sheet of paper ortransparency, creating a developed image. Such high temperatures mayreduce or minimize fuser roll life, such as with fuser rolls made ofsilicone rubbers or fluoroelastomers (e.g., Viton®), may limit fixingspeeds and may necessitate higher power usage during operation, such asin a xerographic copier employing a hot roll fixing mechanism.

Electrophotographic toners are generally prepared by mixing ordispersing a colorant and possibly a charge enhancing additive into athermoplastic binder resin, followed by micropulverization. Known,conventional thermoplastic binder resins include polystyrenes,styreneacrylic resins, styrene-methacrylic resins, polyesters, epoxyresins, acrylics, urethanes and copolymers thereof. Carbon black isoften used as a colorant and alkyl pyridinium halides, distearyldimethyl ammonium methyl sulfate, and the like are often employed ascharge enhancing additives.

Although many processes exist for fixing toner to a support medium, hotroll fixing transfers heat very efficiently and is especially suited forhigh speed electrophotographic processes. In this method, a supportmedium carrying a toner image is transported between a heated fuser rolland a pressure roll with the image face contacting the fuser roll. Uponcontact with the heated fuser roll, the toner melts and adheres to thesupport medium to fix an image.

Toner fixing performance may be characterized as a function oftemperature. The lowest temperature at which the toner adheres to thesupport medium is called the cold offset temperature. The maximumtemperature at which the toner adheres to the fuser roll is called thehot offset temperature. When the fuser temperature exceeds the hotoffset temperature some of the molten toner adheres to the fuser rollduring fixing, is subsequently transferred to a substrate (a phenomenonknown as "offsetting"), and results for example in blurred images.Between the cold offset temperature and hot offset temperature of thetoner is the minimum fix temperature which is the minimum temperature atwhich acceptable adhesion of the toner to the support medium occurs. Thedifference between minimum fix temperature and hot offset temperature iscalled the fusing latitude.

Several problems exist with the hot roll fixing system described aboveand with toners presently used with the system. First, binder resins inthe toners can require a relatively high temperature in order to beaffixed to the support medium. A high temperature may result in highpower consumption, low fixing speeds, and reduced fuser roll and rollbearing life. Offsetting may present a problem.

Toner resins that have a low fix temperature below 200° C. ("low melttoner resin"), preferably below 160° C., and exhibit good offsettemperature performance are desired. Processes for preparing such tonerresins are therefore desirable. Toners operating at lower temperaturesreduce power needs and increase component life. Low melt toners reducevolatilization of release oil such as silicone oil. Volatilization,which may occur during high temperature operation causes problems whenthe volatilized oil condenses on other areas of the machine. Toners withwide fusing latitude permit liberal requirements for oil used as arelease agent. The toners may provide improved particle elasticity andmay minimize copy quality deterioration related to toner offset. Hence,the desirability of low-melt temperature toner resins, particularly foruse in hot-roll fixing xerographic processes, is apparent.

Resins having a lower minimum fix temperature have a lower molecularweight than resins having higher minimum fix temperatures. U.S. Pat. No.3,590,000 to Palermiti et al. and U.S. Pat. No. 3,681,106 to Burns etal. disclose attempts to use polyester resins as a toner binder.Although a minimum fix temperature of polyester binder resins can belower than resins made from other materials, such as styrene-acrylic andstyrene-methacrylic resins, use of polyester resins as toner binder canlead to undesirable lower hot offset temperature. This results in adecreased offset resistance, and a decreased glass transitiontemperature, possibly negatively impacting toner blocking, which occursduring storage.

Resin structure modification by branching, cross-linking, grafting,etc., using conventional polymerization and condensation reactions, mayalso improve offset resistance. Burns et al. discloses mixing atrivalent or more polyol or polyacid with monomer to provide non-linearpolymer modification. Branching during polycondensation results inimproved offset resistance. However, too much branching can result in anincreased minimum fix temperature, diminishing any advantage of themodified polymer.

U.S. Pat. No. 4,533,614 to Fukimoto discloses a non-linearly modifiedlow-melting polyester containing: 1) an alkyl-substituted dicarboxylicacid and/or an alkyl-substituted diol; 2) a trivalent or morepolycarboxylic acid and/or a trivalent or more polyol; 3) a dicarboxylicacid and 4) an etherated diphenol. The main acid component of thepolyester requires 50 mole %, preferably 60 mole % or more, of anaromatic dicarboxylic acid, its analogous anhydride, or otherdicarboxylic acids to impart sufficient electrophotographic chargecharacteristics to a toner made from the resin. Modified polyestershaving less than this amount of aromatic acid do not impart sufficientcharge characteristics.

Heretofore, efforts to produce substantially lower cost, linear,unbranched polyester polymers, exhibiting rheological propertiesrequired for producing high-performing desirable low melt toner resins,have been unsuccessful.

U.S. patent application Ser. No. 07/814,782 discloses linear polyesterbase resins, which may be subsequently cross-linked by a process asdisclosed in U.S. patent application Ser. No. 07/814,641, both toMahabadi et al. The disclosures of these two U.S. patent applicationsare entirely incorporated herein by reference. Mahabadi et al. disclosesa commercially available poly(propoxylated bisphenol A co-fumarate)having a corresponding bisphenol residue in the polyester backbone. Thelinear resins disclosed in these references exhibit desirablerheological properties when cross-linked but are quite costly toproduce.

To reduce product cost while maintaining an equivalent standard ofproduct quality, the inventors have now developed a lower cost polyesterresin, having a different chemical structure than more expensive,commercially available bisphenol based resin products.

SUMMARY OF THE INVENTION

The invention overcomes above-discussed problems in the prior art. Theinvention provides unbranched, linear polyester polymers, capable ofundergoing subsequent cross-linking to obtain high-density, cross-linkedtoner resins for use in toners having improved performance. Ofparticular benefit, the inventive resins may be produced at asubstantially lower cost. The invention provides a thermoplastic resinfor toners, which when cross-linked using known processes exhibitsdesirable rheological properties, rendering the resin useful as a resinin electrophotographic toners. The cross-linked product of the inventivepolymers can be sufficiently fixed at low temperatures (e.g., below 200°C. , preferably below 160° C.) by hot roll fixing. In addition,cross-linked resins prepared from inventive polymers exhibit desirablehot offset and glass transition temperatures. The inventive polymers areparticularly useful as cross-linked toner resins and exhibit excellentcharacteristics comparable with more expensive commercially availablecross-linked resins.

The inventive polyester polymer is a low cost, unsaturated linearpolymer. The linear polymer may be a reaction product of atransesterification or other conventional process. The reaction productis a polymerization reaction product of first, second, third, andoptionally fourth, monomers. The reaction product has first, second,third, and optionally fourth, residues derived from each of the first,second, third and fourth monomers, respectively. The inventive polymerhas a glass transition temperature ranging from about 52° C. to about61° C. The polymer has a first residue of a diol having a molecularweight below about 200 and has a second residue from a monomer, whichmay be a unsaturated dicarboxylic acid, a diester, or an anhydridethereof. The second residue concentration ranges from about 3 wt. % toabout 15 wt. %, based on the total weight of the polymer. The thirdmonomer may be an aromatic dicarboxylic acid, or a diester thereof. Thethird residue concentration in the polymer ranges from about 40 wt. % toabout 50 wt. %, based on the total weight of the polymer.

In a process for preparing the unsaturated, linear polymer, the first,second and third monomers are polymerized at a reaction temperature andfor a reaction time to form the inventive linear polymer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates rheology curves for a known linear base resin andcorresponding cross-linked resins.

FIG. 2 illustrates a rheology curve for a control linear polymer used asa source of comparative data and rheology curves for correspondingcross-linked resins.

FIG. 3 illustrates rheology curves for an inventive polymer,cross-linked using various percentages of cross-linking initiator.

FIG. 4 illustrates rheology curves for an alternative, preferredembodiment of the inventive polymer, cross-linked using varying amountsof a cross-linking initiator.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The inventive unsaturated, linear polymer is a much lower-costalternative than comparable, commercially available resins. Theinventive resin achieves economy without compromising physicalproperties required of cross-linked toner resins for use in highperforming toners. The inventive polymer and cross-linked toner resinsmade therefrom exhibit rheological behavior comparable with highperforming resins. Toners made from the inventive cross-linked resinsexhibit desirable low minimum fix temperatures. In addition, theinventive polymer, when cross-linked and incorporated into a toner,exhibits good offset properties and wide fusing latitudes as comparedwith conventional, more expensive, cross-linked resins. The inventivenon-linearly modified, unbranched polymer does not suffer fromdisadvantages of earlier resins.

Applicants have developed a linear-modified polyester polymer, whichwhen subsequently cross-linked using a representative cross-linkingprocess, such as disclosed for example in Mahabadi et al., does notcompromise characteristics required of toners used in conventionalhot-roll fixing systems. The low-melt linear polyester polymer hasrepeating units of a reaction product of a first monomer, a secondmonomer, a third monomer, and optionally a fourth monomer. The polymerhas first, second, third, and optionally fourth residues, derived fromeach of the first, second, third and fourth monomers, respectively. Toprovide desirable properties of conventional polyester resins used intoners, the inventive polymer has a glass transition temperature rangingfrom about 52° C. to about 61° C., preferably 57°-59° C. The firstmonomer preferably has a weight average molecular weight (M_(w)) lessthan about 200. The second monomer may be an unsaturatd dicarboxylicacid, of diester, or a anhydride thereof. The second residue isincorporated into the polymer such that a concentration of the secondresidue ranges from about 3 wt. % to about 15 wt. %, preferably fromabout 5 to 8 wt. %, based on the total weight of the polymer. The thirdmonomer may be an aromatic dicarboxylic acid or a diester thereof, whichmay be different from the second monomer. The aromatic dicarboxyclicacid or diester is incorporated into the polyester polymer such that thethird residue (originating from the third monomer) is present in aconcentration ranging from about 40 wt. % to about 50wt. %, based on thetotal weight of the polymer.

The inventive polymers and resulting resins contain residues, of anunbranched, linear aliphatic diol as a first residue in the polyesterbackbone. The first monomer is reacted with the second monomer and anaromatic dicarboxylic acid or ester (third monomer) to obtain a morecost effective resin having the required rheological properties andphysical characteristics.

In the inventive resin, second residues (derived from the secondmonomer) may be present in a concentration which ranges from about 3 wt.% to about 8 wt. %. The inventive polyester resins have lowerconcentrations of second residues and are prepared at a lower cost thanknown linear resins. Toner resins made from the inventive polymersimpart unexpected desirable toner blocking performance to toners madefrom the resulting resins.

The low fix temperature of resins prepared from the inventive polymersis a function of the molecular weight and molecular weight distributionof linear portion. However, the preferred lower molecular weight diolsin the inventive polymers may also have an undesirable lowering effecton the polymer's glass transition temperature. The third monomer isincorporated into the polyester backbone to achieve a glass transitiontemperature that approximates transition temperatures required ofconventional polymers. Thus, the inventive polymers do not suffer frompoor performance due to an unacceptably low glass transitiontemperature.

Also, in some of the inventive polyester polymers, the lower cost firstresidue of the backbone may have a lowering effect on polymer's glasstransition temperature, (sometimes to border-line levels). A highermolecular weight alcohol (fourth monomer) may be added to the monomerreaction mixture during preparation to compensate for the lower-weightfirst residue (diol) component of the polyester backbone. The molecularweight of the fourth monomer should be higher than the molecular weightof the first monomer. To ensure good blocking performance incross-linked resins prepared from the inventive polymers, the glasstransition temperature of the inventive polymers may be raised fromabout 2° to about 5° C. by additionally incorporating from about 1 toabout 20 mole percent, based on the total diol residue in the polyesterpolymer, of higher molecular weight fourth monomer. The fourth monomercompensates for an undesirably low glass transition temperature withoutsignificantly increasing the cost of the inventive polymer.

Exemplary first monomers useful in preparing polymers according to theinvention include, but are not limited to 1,2-propane diol,1,3-butanediol, ethylene glycol, 1,4-butanediol, diethylene glycol,neopentyl glycol, dipropylene glycol, dibromoneopentyl glycol,2,2,4-trimethylpentane-1,3-diol, 1,4-butanediol and the like andmixtures thereof. The diol residue of the polymer should be present inthe inventive polymer in a concentration ranging from 42% to 78%,preferably from about 50-65%, and more preferably from 55-60% by weight,based on the total weight of the resulting polymer.

Exemplary second monomers include, but are not limited to, dicarboxylicacids or esters of dicarboxylic acids, such as for example, maleic acid,maleic anhydride, fumaric acid, chloromaleic acid, itaconic acid,citraconic acid, mesaconic acid, esters thereof and the like.

The concentration of the third residue derived from the third monomershould range from about 40% to about 50% by weight, based on the totalweight of the resulting polymer. Too much of the third residue in thefinal polymer may adversely affect the polymer's rheological properties.Exemplary aromatic dicarboxylic acids and esters of acids used as thirdmonomers in preparing the inventive polymers include, but are notlimited to, terephthalic acid, isophthalic acid, phthalic acid,benzophenone-4,4'-dicarboxylic acid,1,2-diphenoxyethane-p,p'-dicarboxylic acid, tetrahydrophthalic acid,phthalic anhydride, chlorendic anhydride, tetrahydrophthalic anhydride,hexahydrophthalic anhydride, endomethylene tetrahydrophthalic anhydride,tetrachlorophthalic anhydride, tetrabromophthalic anhydride,their estersand the like. A preferred ester of terephthalic acid is dimethylterephthalate.

Exemplary fourth monomers include, but are not limited to, propoxylatedbisphenol A, ethoxylated bisphenol A, tetrabromo bisphenol dipropoxyether and the like and mixtures thereof. Again, the fourth monomershould have a molecular weight higher than that of the first monomer.

The inventive polymers may be manufactured by step-wise reaction betweenthe first, second and third monomers, preferably with a fourth monomeras described above. The resulting unsaturated polyesters are reactive(e.g., cross-linkable) at: (i) unsaturation sites (double bonds) alongthe polyester chain, and (ii) functional groups such as carboxyl,hydroxy, etc. groups amenable to acid-base reactions.

In a process for preparing the inventive unsaturated linear polymer, areaction vessel is used to condense the first and second monomers. Thefirst and second monomers, preferably with the transition monomer andfourth monomer, are placed in the reactor. The monomers are thoroughlymixed to form a homogeneous solution. The solution is heated to atemperature at which a clear melt of the starting monomers is obtained,at which time a catalyst may be added to promote transesterification.Volatile alcohol by-product from transesterification (e.g. methanol orethanol)is removed from the reaction system until more than 90% of thetheoretical volatile alcohol has been removed.

Transesterification catalysts may include, but are not limited to,tetraisopropyl orthotitanate transesterification catalyst, tetrabutylorthotitanate monobutyl tin oxide (e.g., FASCAT 4100, a registeredtrademark of M&T Chemicals Inc.), dibutyl tin oxide, and othertransesterification catalysts used by those skilled in the art ofpolyester synthesis. Transesterification temperatures range from about150° to 250° C., preferably from about 185° C. to about 215° C. Excessdiol monomer should be removed under generated vacuum. Total reactiontimes may range from about 1 to about 5 hours.

Reaction mechanisms for preparing the inventive polymers may include thefollowing mechanisms for an exemplary embodiment of the invention:##STR1##

Methanol is eliminated and the reaction continues until substantiallyall of the second monomer or Third monomer has reacted with the firstmonomer. Since the second monomer is reacted at a far lowerconcentration than the third monomer, there will be a higher percentageof the third residues in the polymer contributed by the third monomer.The third residue is exemplified structurally as follows: ##STR2## "n"representing the number of repeating units. The second residuecontributed by the second monomer will appear far more randomly in thepolymer backbone. The second residue appears in the polymer as nrepeating units of the following polymer unit, alternating randomly withthe above polymer unit. ##STR3##

Thus, a single exemplary polymer unit of the invention may resemble thefollowing structure, n being the number of polymer repeating units:##STR4##

The weight average molecular weight, M_(w), of the inventive polymer,may be in the range of about 5,000 to 20,000 and the number averagemolecular weight, M_(n), of the inventive polymer, may be in the rangeof about 2,000 to about 6,000.

The linear inventive polymer may be cross-linked using knowncross-linking reactions.

Densely cross-linked toner resins may be cross-linked by a reactiveextrusion process, the resulting resins comprising cross-linked portionsand linear portions. Reactively extruded polymer resins of the inventioncomprise very high molecular weight, densely cross-linked microgelparticles, insoluble in substantially any solvent, includingtetrahydrofuran, toluene and the like. The linear portion comprises lowmolecular weight resin soluble in various solvents such as for exampletetrahydrofuran, toluene and the like. High molecular weight, highlycross-linked gel particles are substantially uniformly distributed inthe linear portions. Substantially no portion of the resin, cross-linkedby reactive extrusion, comprises sol (low density cross-linked polymer),such as that which would be obtained in cross-linking processes such aspolycondensation, bulk, solution, suspension, emulsion and dispersionpolymerization processes.

Resins prepared from the inventive polymers are generally present in atoner made from the inventive polymers in an amount of from about 40 toabout 98 percent by weight, and more preferably from about 70 to about98 percent by weight. They may be present in greater or lesser amounts,provided that the objectives of the invention are achieved. Toner resinsprepared from polymers may be subsequently melt blended or otherwisemixed with a colorant, charge carrier additives, surfactants,emulsifiers, pigment dispersants, flow additives, and the like. Thetoner product can then be pulverized by known methods such as milling toform toner particles. The toner particles preferably have an averagevolume particle diameter of about 5 to about 25, more preferably about 5to about 15, microns.

Various suitable colorants can be employed in toners of the invention,including suitable colored pigments, dyes, and mixtures thereof,including Carbon Black, such as Regal 330® carbon black (Cabot),Acetylene Black, Lamp Black, Aniline Black, Chrome Yellow, Zinc Yellow,Sicofast Yellow, Luna Yellow, Novaperm Yellow, Chrome Orange, BayplastOrange, Cadmium Red, Lithol Scarlet, Hostaperm Red, Fanal Pink,Hostaperm Pink, Lithol Red, Rhodamine Lake B, Brilliant Carmine,Heliogen Blue, Hostaperm Blue, Neopan Blue, PV Fast Blue, CinquassiGreen, Hostaperm Green, titanium dioxide, cobalt, nickel, iron powder,Sicopur 4068 FF and iron oxides, such as Mapico Black (Columbia), NP608and NP604 (Northern Pigment), Bayferrox 8610 (Bayer), MO8699 (Mobay),TMB-100 (Magnox), mixtures thereof and the like.

The colorant, preferably carbon black, cyan, magenta and/or yellowcolorant, is incorporated in an amount sufficient to impart the desiredcolor to the toner. In general, pigment or dye is employed in an amountranging from about 2 to about 60 percent by weight, and preferably fromabout 2 to about 7 percent by weight for color toner and about 5 toabout 60 percent by weight for black toner.

Various known suitable effective positive or negative charge enhancingadditives can be selected for incorporation into the toner compositionsprepared using the inventive polymers, preferably in an amount of about0.1 to about 10, more preferably about 1 to about 3, percent by weight.Examples include quaternary ammonium compounds inclusive of alkylpyridinium halides; alkyl pyridinium compounds; organic sulfate andsulfonate compositions; cetyl pyridinium tetrafluoroborates; disteatyldimethyl ammonium methyl sulfate; aluminum salts such as Bontron E84™ orE88™ (Hodogaya Chemical); and the like.

Additionally, other internal and/or external additives may be added inknown amounts to impart known functions to the resulting toners. Theselected carrier particles can be used with or without a coating, thecoating generally being comprised of fluoropolymers, such aspolyvinylidene fluoride resins, terpolymers of styrene, methylmethacrylate, and a silane, such as triethoxy silane,tetrafluoroethytenes, other known coatings and the like.

The toners or developers made from the inventive polymers can becharged, e.g., triboelectrically, and applied to an oppositely chargedlatent image on an imaging member such as a photoreceptor or ionographicreceiver. The resultant toner image can then be transferred, eitherdirectly or via an intermediate transport member, to a support such aspaper or a transparency sheet. The toner image can be fused to thesupport by application of heat and/or pressure, for example with aheated fuser roll at a temperature lower than 200° C., preferably lowerthan 160° C., more preferably lower than 140° C., and more preferablyabout 110° C.

While the invention has been described with reference to particularpreferred embodiments, the invention is not limited to the specificexamples given. Other embodiments and modifications can be made by thoseskilled in the art without departing from the spirit and scope of theinvention.

EXAMPLE I

A poly(1,2-propyleneterephthalate/1,2-propylenefumarate) copolymer isprepared by the following procedure. A 3 liter glass reactor isassembled with a stainless steel helical anchor stirrer and high vacuumstirrer bearing adaptor, glass thermometer well and 250° C. thermometer,inert gas inlet adaptor, water-jacketed vigreux column fixed with a DeanStark trap and condenser, and a full length heating mantle controlledwith a 12R Thermowatch Regulator attached to the thermometer.

1815.77 grams (9.35 moles) of dimethylterephthalate, 1673.98 grams (22.0moles) of 1,2-propane diol, and 284.13 grams (1.65 moles) ofdimethylfumarate are added to the reactor. After the reactor and itscontents reach 135° C. by heating with the mantle, a clear melt isobtained. The clear melt is argon sparged for approximately 20 minutesto remove dissolved oxygen. At this point 5.34 grams (0.018 moles) oftitanium(IV) isopropoxide transesterification catalyst is added topromote transesterification.

Methanol is then removed by the Dean Stark trap/condenser system until650 grams of the volatile alcohol (92% theoretical) are removed. At thistime the reactor is connected to a high vacuum trap system with twoinline dry ice traps, and the reactor contents are raised to 200° C.Vacuum is slowly applied to remove excess 1,2-propane diol, after whichfull vacuum is obtained at 200 microns. After one hour and 20 minutes, asample is analyzed and found to have a melt index of 78.0 (grams per tenminutes) at 105° C./2.160 kilograms and a Tg of 54° C., obtained using aPerkin Elmer DSC-4. Gel permeation chromatography of the polymerconfirmed a M_(w) of 6,400, M_(n) of 3,100 and a MWD of 2.3 .Theconcentration of unsaturated units is approximately 6 wt. % of theresin. The unsaturated, functional units are contributed by thefumarate. At this point the main batch of polymer is removed from thereactor.

The polymer is cross-linked using 0.5% and 1.0% benzoyl peroxidecross-linking initiator in a reactive extrusion process as disclosed inMahabadi et al., supra and rheology data is measured and plotted for thelinear and cross-linked polymers as shown in FIG. 3. Rheology plot Arepresents viscosity of the inventive polymer. Rheology plot Brepresents viscosity of a resin of the inventive polymer cross-linkedusing 0.5% benzoyl peroxide at 160° C. The cross-linked resin exhibitshigher viscosity at higher temperature. Similarly, the rheology plot Crepresents viscosity of a resin of the inventive polymer, cross-linkedusing 1.0% benzoyl peroxide. The effect of a higher benzoyl peroxideconcentration results in a higher viscosity at higher temperatures. Theresults indicate resin performance consistent with desired values forlow-fix temperature conventional toner resins, shown in FIG. 1. In FIG.1, curve F represents rheology of a commercially available linear resin.Curves G and H are plotted rheology data for cross-linked, conventionalpolyester polymers.

EXAMPLE II

A poly(1,2-propyleneterephthalate/1,2-propylenefumarate) polymer isprepared by the procedure of Example I using the conditions discussedtherein except that 1481 grams (19.7 moles) of 1,2-propane diol, 2142grams (11.03 moles) of dimethylterephthalate and 397.8 grams (2.76moles) of dimethylfumarate are added to the reactor and mixed whileheating to obtain the clear melt The clear melt is argon sparged forapproximately 20 minutes to remove dissolved oxygen. At this point 6.31grams (0.022 moles) of titanium(IV) isopropoxide transesterificationcatalyst is added to promote transesterification.

Methanol is then removed by the Dean Stark trap/condenser system until650 grams of the volatile alcohol (83% theoretical) are removed. At thistime the reactor is connected to a high vacuum trap system with twoinline dry ice traps, and the reactor contents are raised to 200° C.Vacuum is slowly applied to remove excess 1,2-propane diol, after whichfull vacuum is obtained at about 200 microns. Analysis reveals that theresulting linear polyester polymer has a glass transition temperature of52° C. and a melt index of 101 at 117° C. per 2.160 kilograms. Gelpermeation chromatography of the polymer confirms a M_(w) of 7,500,M_(n) of 2,600 and a MWD of 2.88. The concentration of unsaturated unitsis approximately 8 wt. % of the resin. The unsaturated, functional unitsare contributed by the fumarate. The polymer is cross-linked usingreactive extrusion and rheological tests are conducted. Data measuredand plotted is shown in FIG. 4. Rheology plots B, C and D representviscosities of resins cross-linked using 0.25%, 0.3% and 0.5% benzoylperoxide, respectively, in the reactive extrusion processes. A higherpercentage of benzoyl peroxide yields denser cross-linking and, thus,increased viscosities at higher temperatures. The rheological featuresof the inventive copolymer patterns favorably compare with conventionalresins, again as shown in FIG. 1.

EXAMPLE III

A commercialy prepared poly(propoxylated bisphenol A-cofumarate)polymer, refered to as virgin Spar II, is shown here for comparison. Theresin was found to have a melt index of 52 grams per ten minutes at 117°C./2.160 Kg and a Tg of 55.4° C., as measured on a Perkin Elmer DSC-4.Gel permeation chromatography of the polymer confirmed a M_(w) of13,200, M_(n) of 6,200 and a MWD of 2.1 . This polymer is representativeof a commercialy prepared poly(propoxylated bisphenol A fumarate)polymer.

EXAMPLE IV COMPARATIVE EXAMPLE

A laboratory prepared polymer of poly(propoxylated bisphenol A fumarate)is synthesized by the following procedure. A 3 liter glass reactor isassembled with the reaction system components as specified in Example I.To the reactor is added 1613.00 grams (4.689 moles) of propoxylatedbisphenol A (SYN FAC 8029 obtained from Milliken Chemicals), and 557.0grams (4.798 moles) of fumaric acid. After the reactor and its contentsreach 135° C., the obtained slurry is argon sparged for approximately 20minutes to remove dissolved oxygen. Heating is allowed to continue toaproximetly 190° C.

Water from esterification is removed using the Dean Stark trap/condensersystem until 145 grams (about 74% of theoretical) of water is removed.At this time the reactor is connected to the high vacuum trap systemwith two inline dry ice traps and the reactor contents raised to 200° C.A vacuum is slowly applied and maintained at about 50 microns. Afterthree hours and twenty minutes, the resin is removed from the reactor.Upon analysis it has a melt index of 62 grams per ten minutes at 117°C./2.160 Kg and a Tg of 55° C. as measured on a Perkin Elmer DSC-4. Gelpermeation chromatography of the polymer confirms a M_(w) of 15,000,M_(n) of 3,900 and a MWD of 3.8.

Rheology results of the comparative polymer and correspondingcross-linked resins, cross-linked in a reactive extrusion process, areillustrated in FIG. 2. Rheology of the comparative resin anduncross-linked comparative polymer parallels that of resins preparedusing the inventive polymers. Rheology plot A corresponds to viscosityof the uncross-linked polymer at various temperatures. Rheology plot Bcorresponds to viscosity of the cross-linked comparative polymer using0.25% benzoyl peroxide at 160° C. in a reactive extrusion process.

EXAMPLE V

A poly(1,2-propyleneterephthalate/1,2-propylenefumarate) polymer isprepared by the procedure in Example I using the conditions discussedtherein except that 1481 grams (19.7 moles) of 1,2-propane diol, 2142grams (11.03 moles) of dimethylterephthalate and 397.8 grams (2.76moles) of dimethylfumarate are added to the reactor and mixed whileheating to obtain the clear melt. The clear melt is argon sparged forapproximately 20 minutes to remove dissolved oxygen. At this point 6.31grams (0.0222 moles) of titanium(iV) isopropoxide transesterificationcatalyst is added to promote transesterification.

Methanol is removed by the Dean Stark trap/condenser system until 650grams of the volatile alcohol (95% theoretical) are removed. At thistime the reactor is connected to a high vacuum trap system with twoinline dry ice traps, and the reactor contents are raised to 200° C.Vacuum is slowly applied to remove excess 1,2-propane diol, after whichfull vacuum is obtained at about 100 microns. During one hundred fortyeight minutes of total vacuum, one sample is taken at 127 minutes, andanother sample at the end of the total vacuum time. The first sample isfound to have a melt index of 20.8 grams per ten minutes at 117°C./2.160 Kg and a Tg of 58.5° C., as measured on a Perkin Elmer DSC-4.Gel permeation chromatography of the polymer confirms a M_(w) of 8,400,M_(n) of 3,100 and a MWD of 2.7. The last sample, which is the bulk ofthe polymer, has a melt index of 9.4 grams per ten minutes at 117°C./2.160 Kg and a Tg of 61.3° C., as measured on a Perkin Elmer DSC-4.Gel permeation chromatography of the polymer confirms a M_(w) of 10,000,a M_(n) of 3,800 and a MWD of 2.6. The concentration of unsaturatedunits is approximately 8 wt. % of the resin. These unsaturated,functional units are contributed by the fumarate. These polymersrepresent lower melt index properties and higher Tg resins that arecapable of being crosslinked by reactive extrusion methods as in ExampleI & II.

EXAMPLE VI

An unsaturated-polyester of propoxylated bisphenol A and 1,2-propanediols is prepared by the procedure in Example I using the conditionsdiscussed therein except that 1346 grams (17.58 moles) of 1,2-propanediol, 1606 grams (8.27 moles) of dimethylterephthalate, 364 grams (2.07moles) of diethylfumarate and 534 grams (1.55 moles) of propoxylatedbisphenol A (SYNFAC 8029 obtained from Milliken Chemicals), are added tothe reactor and mixed while heating to obtain a clear melt. The clearmelt is argon sparged for approximately 20 minutes to remove dissolvedoxygen. At this point 5.83 grams (0.0205 moles) of titanium(IV)isopropoxide transesterification catalyst is added to promotetransesterification.

Methanol and ethanol byproduct is removed by the Dean Starktrap/condenser system until 95% theoretical is obtained. At this timethe reactor is connected to a high vacuum trap system with two inlinedry ice traps, and the reactor contents are raised to 200° C. Vacuum isslowly applied to remove excess 1,2-propane diol, after which fullvacuum is obtained at about 400 microns. After two hours and twenty fourminutes of vacuum, the polymer is removed from the reactor. Uponcharacterization the polymer is found to have a melt index of₋₋ 84.0₋₋grams per ten minutes at 117° C./2.160 Kg and a Tg of 54.5° C., asmeasured on a Perkin Elmer DSC-4. Gel permeation chromatography of thepolymer confirms a M_(w) of 7,500, M_(n) of 2,700 and a MWD of 2.7. Theconcentration of unsaturated units is approximately 8 wt. % of theresin. These unsaturated, functional units are contributed by thefumarate. The resin is capable of being crosslinked by reactiveextrusion methods as in Example II.

EXAMPLE VII

An unsaturated-polyester is prepared using both 1,2-propane diol. and1,3-butane diol by the procedure in Example I. Using the conditionsdiscussed in Example I, 1481.) grams (19.47 moles) of 1,2-propane diol,2142.0 grams (11.03 moles) of dimethylterephthalate, 397.8 grams (2.76moles) of dimethylfumarate and 111.0 grams (1.23 moles) of 1,3-butanediol, are added to a reactor and mixed while heating to obtaina clearmelt. The clear melt is argon sparged for approximately 20 minutes toremove dissolved oxygen. At this point 6.21 grams (0.0218 moles) oftitanium(IV) isopropoxide transesterification catalyst is added topromote transesterification.

Methanol byproduct is removed by the Dean Stark trap/condenser systemuntil 86.8% theoretical is obtained. At this time the reactor isconnected to a high vacuum trap system with two inline dry ice traps,and the reactor contents are raised to 200° C. Vacuum is slowly appliedto remove excess diols, after which full vacuum is obtained at about 110microns. After three hours and fifty five minutes of total vacuum, thepolymer is removed from the reactor. Upon characterization the polymeris found to have a melt index of 50.5 grams per ten minutes at 117°C./2.160 Kg and a Tg of 56.0° C., as measured on a Perkin Elmer DSC-4.Gel permeation chromatography of the polymer confirms a M_(w) of 9,100,M_(n) of 3,500 and a MWD of 2.6. The concentration of unsaturated unitsis approximately 8 wt. % of the resin. These unsaturated, functionalunits are contributed by the fumarate. The resin is capable of beingcrosslinked by reactive extrusion methods as in Example II.

EXAMPLE VIII

An unsaturated-polyester is prepared using 1,2-propane diol, ethanediol,dimethyl terephthalate and dimethylfumarate.

Dimethyl terephthalate (1692 g), dimethylfumarate (208 g),1,2-propanediol (1641 g), 1,2-ethanediol (148.8 g) and Fascat (3.2 g)are charged into a 7.6 liter Parr reactor equipped with a double turbineagitator and distillation aparatus. The reactor is heated to 165° C.,and stirred at 200 rpm, followed by increasing the temperature slowly to180° C. over a 3 hour period, during which 545 grams of methanol iscollected in the distillation reciever. The mixture is then heated to190° C. over a 1 hour period, followed by decreasing the pressure to 0.5millibarrs over a 3 hour period, during which time an additional 664grams of byproduct is collected in the distillation reciever. Thereactor is then pressurized to atmospheric pressure with CO₂, and theproduct is discharged through the bottom drain valve into a metal dish.After the product is cooled to room temperature, the glass transitiontemperature of the unsaturated polyester is found to be 57.8° C.

EXAMPLE IX

An unsaturated-polyester is prepared using 1,2-propane diol.,ethanediol, terephthalic acid and fumaric acid.

Terephthalic acid (564 g), fumaric acid (69.6 g), 1,2-ethanediol (49.6g), 1,2-propanediol (547.2 g) and Fascat (3.2 g) are charged into aHoppes 2 liter pressure reactor equipped with a helical agitator anddistillation aparatus. The mixture is heated to 240° C. under 420killopascal pressure utilizing CO₂ gas. The mixture is stirred at 60 rpmfor 4 hours, followed by decreasing the temperature to 220° C., andpressure to atmospheric pressure over a four hour period. The reactorpressure is then decreased to 0.5 miilibarrs over a 3 hour period,during which time an additional 664 grams of byproduct is collected inthe distillation reciever. The reactor is then pressurized toatmospheric pressure with CO₂, and the product is discharged through thebottom drain valve into a metal dish. After the product is cooled toroom temperature, the glass transition temperature of the unsaturatedpolyester is found to be 52° C.

EXAMPLE X

An unsaturated-polyester is prepared using 1,2-propane diol.,ethanediol, terephthalic acid and fumaric acid.

Terephthalic acid (564 g), fumaric acid (69.6 g), 1,2-ethanediol (49.6g), 1,2-propanediol (547.2 g) and Fascat (3.2 g) are charged into theHoppes 2 liter pressure reactor equipped with a helical agitator anddistillation aparatus. The mixture is heated to 240° C. under 420killopascal pressure utilizing CO₂ gas. The mixture is stirred at 60 rpmfor 4 hours, followed by decreasing the temperature to 220° C., andpressure to atmospheric pressure over a four hour period. The reactorpressure is then decreased to 0.5 millibarrs over a 3 hour period,during which time an additional 664 grams of byproduct is collected inthe distillation reciever, followed by maintaining the pressure at 0.5millibarrs for an additional hour. The reactor is then pressurized toatmospheric pressure with CO₂, and the product is discharged through thebottom drain valve into a metal dish. After the product is cooled toroom temperature, the glass transition temperature of the unsaturatedpolyester is found to be 62° C.

EXAMPLE XI

A Black toner composition of 94 percent by weight crosslinked polyester,derived from the unsaturated polyester resin of Example VIII, withbenzoyl peroxide and with 6 percent by weight of Regal 330 blackpigment, is prepared as follows.

The unsaturated polyester resin of Example VIII (58 grams) and benzoylperoxide L-78 (0.85 g) is charged into a Haake melt mixer B-135available from HBI System. The melt mixer is then heated to 160° C. at arotational mixing speed of 100 revolutions per minute for a duration of15 minutes. The reaction mixture is then cooled to room temperature. Thecrosslinked polyester is then milled in a coffee blender with 3.7 gramsof Regal 330, and heated in the Haake melt mixer to 120° C. at 100 rpmfor a duration of 15 minutes. The composite mixture is cooled to roomtemperature, and milled broken into coarse particles utilizing a coffeebean grinder available from Black and Decker. An 8 inch Struteventmicronizer is used to reduce the particle size further. After grinding,the toner is measured to display an average volume diameter particlesize of 7.8 microns with a geometric distribution of 1.39 as measured bythe Coulter Counter. The resulting toner is then utilized withoutfurther classification.

A developer composition is prepared by roll milling the aforementionedtoner, 3 parts by weight, with 100 parts by weight of carrier having asteel core with polyvinylidene polymer coating. Tribo data is obtainedusing the known blow-off Faraday Cage apparatus. The toner developer issubjected to 20 percent humidity in a chamber for 48 hours, and to 80percent humidity level in a chamber for 48 hours. The ratio of thecorresponding triboelectric charge at 20 percent RH to 80 percent RH asgiven by equation 1, is measured to be 2.3. Unfused copies were thenproduced using a Xerox Corporation 1075 imaging aparatus with the fusingsystem disabled. The unfused copies are then fused on a 1075 fuser usinga process speed of 11.9 inches per second. Fusing evaluation of thetoner indicates a minimum fixing temperature of about 140° C., andhot-offset temperature of 175° C.

EXAMPLE XII

A Black toner composition of 94 percent by weight crosslinked polyester,derived from the unsaturated polyester resin of Example IX, with benzoylperoxide and with 6 percent by weight of Regal 330 black pigment, isprepared as follows.

The unsaturated polyester resin of Example IX (58 grams) and benzoylperoxide L-78 (0.85 g) are charged into a Haake melt mixer B-135available from HBI System. The melt mixer is heated to 160° C. at arotational mixing speed of 100 revolutions per minute for a duration of15 minutes. The reaction mixture is then cooled to room temperature. Thecrosslinked polyester is then milled in a coffee blender with 3.7 gramsof Regal 330, and heated in the Haake melt mixer to 120° C. at 100 rpmfor a duration of 15 minutes. The composite mixture is then cooled toroom temperature, and milled broken into coarse particles utilizing acoffee bean grinder available from Black and Decker. An 8 inchStrutevent micronizer is used to reduce the particle size further. Aftergrinding, the toner is measured to display an average volume diameterparticle size of 6.9 microns with a geometric distribution of 1.38 asmeasured by the Coulter Counter. The resulting toner is then utilizedwithout further classification.

A developer composition is prepared by roll milling the aforementionedtoner, 3 parts by weight, with 100 parts by weight of a carrier of steelcore with polyvinylidene polymer coating. Tribo data is obtained usingthe known blow-off Faraday Cage apparatus, and the toner developer issubjected to 20 percent humidity in a chamber for 48 hours, and to 80percent humidity level in a chamber for 48 hours. The ratio of thecorresponding triboelectric charge at 20 percent RH to 80 percent RH asgiven by equation 1, is measured to be 2.3. Unfused copies are producedusing a Xerox Corporation 1075 imaging aparatus with the fusing systemdisabled. The unfused copies are then fused on a 1075 fuser using aprocess speed of 11.9 inches per second. Fusing evaluation of the tonerindicates a minimum fixing temperature of about 134° C., and hot-offsettemperature of 165° C.

EXAMPLE XIII

A Black toner composition of 94 percent by weight crosslinked polyester,derived from the unsaturated polyester resin of Example X, with benzoylperoxide and with 6 percent by weight of Regal 330 black pigment, isprepared as follows.

The unsaturated polyester resin of Example X (58 grams) and benzoylperoxide L-78 (0.85 g) are charged into a Haake melt mixer B-135available from HBI System. The melt mixer is heated to 160° C. at arotational mixing speed of 100 revolutions per minute for a duration of15 minutes. The reaction mixture is cooled to room temperature. Thecrosslinked polyester is milled in a coffee blender with 3.7 grams ofRegal 330, and heated in the Haake melt mixer to 120° C. at 100 rpm fora duration of 15 minutes. The composite mixture is cooled to roomtemperature, and mill broken into coarse particles utilizing a coffeebean grinder available from Black and Decher. An 8 inch Struteventmicronizer is used to reduce the particle size further. After grinding,the toner is measured to display an average volume diameter particlesize of 8.1 microns with a geometric distribution of 1.36 as measured bythe Coulter Counter. The resulting toner is utilized without furtherclassification.

A developer composition is prepared by roll milling the aforementionedtoner, 3 parts by weight, with 100 parts by weight of a carrier of steelcore with polyvinylidene polymer coating. Tribo data is obtained usingthe known blow-off Faraday Cage apparatus, and the toner developer issubjected to 20 percent humidity in a chamber for 48 hours, and at 80percent humidity level in a chamber for 48 hours. The ratio of thecorresponding triboelectric charge at 20 percent RH to 80 percent RH, ismeasured to be 2.3. Unfused copies are then produced using a XeroxCorporation 1075 imaging apparatus with fusing system disabled. Theunfused copies are fused on a 1075 fuser using a process speed of 11.9inches per second. Fusing evaluation of the toner indicates a minimumfixing temperature of about 147° C., and hot-offset temperature of 180°C.

What is claimed is:
 1. An unsaturated linear polymer comprising: areaction product comprising first residues of a first monomer, secondresidues of a second monomer and third residues of a third monomer, saidfirst monomer being a diol having a molecular weight below about 200,said second monomer being selected from the group consisting ofunsaturated dicarboxylic acids and diesters, and said third monomerbeing different from said second monomer and selected from the groupconsisting of aromatic dicarboxylic acids and diesters; a concentrationof said second residues ranging from about 3 to about 15 wt. %, based ona total weight of the polymer, and a concentration of said thirdresidues ranging from about 40 to about 50 wt. % based on a total weightof the polymer; said polymer having a glass transition temperatureranging from about 52° C. to about 61° C.
 2. The polymer according toclaim 1, wherein the weight average molecular weight, M_(w), is in therange of about 5,000 to 20,000 and the number average molecular weight,M_(n), is in the range of about 2,000 to 6,000.
 3. The polymer accordingto claim 1, wherein the glass transition temperature ranges from about57° C. to about 59° C.
 4. The polymer according to claim 1, wherein theconcentration of second residues in the polymer ranges from about 5 wt.% to about 8 wt. %, based on the total weight of the polymer.
 5. Thepolymer according to claim 1, wherein the concentration of firstresidues in the polymer ranges from about 42 wt. % to about 78 wt. %,based on the total weight of the polymer.
 6. The polymer according toclaim 4, wherein the first residue concentration ranges from about 50wt. % to about 65 wt. % based on the total weight of the polymer.
 7. Thepolymer according to claim 4, wherein the first residue concentrationranges from about 55 wt. % to about 60 wt. % based on the total weightof the polymer.
 8. The polymer according to claim 1, wherein the firstmonomer is selected from the group consisting of 1,2-propane diol,1,3-butane diol, ethylene glycol, 1,4-butane diol, diethylene glycol,neopentyl glycol, dipropylene glycol, dibromo neopentyl glycol,2,2,4-trimethyl pentane-1,3-diol, 1,4-butane diol and mixtures thereof.9. The polymer according to claim 1, wherein the second monomer isselected from the group consisting of maleic acid, maleic anhydride,fumaric acid, chloromaleic acid, itaconic acid, citraconic acid,mesaconic acid and esters and anhydrides thereof.
 10. The polymeraccording to claim 1, wherein the third monomer is selected from thegroup consisting of terephthalic acid, isophthalic acid, phthalic acid,benzophenone-4-4'-dicarboxylic acid,1,2-diphenoxyethane-p,p'-dicarboxylic acid, naphthalene dicarboxylicacid, tetrahydrophthalic acid, phthalic anhydride, chlorendic anhydride,tetrahydrophthalic anhydride, hexahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, tetrachlorophthalic anhydride, tetrabromophthalic anhydride and esters thereof.
 11. The polymer according toclaim 1, wherein the first monomer is 1,2-propane diol, the secondmonomer is diethyl fumarate and the third monomer is dimethylterephthalate.
 12. The polymer according to claim 1, wherein the polymeris cross-linked to form a polyester toner resin consisting essentiallyof high density cross-linked microgel particles and linear polymer. 13.The polymer according to claim 1, wherein the polyester toner resin issubstantially free of sol.
 14. The polymer according to claim 1, furthercomprising from about 1 to about 20 mole percent, based on a total diolresidue in the polymer, of fourth residues derived from a fourth monomerbeing a diol having a higher molecular weight than said first monomer.15. The polymer according to claim 14, wherein the fourth monomer isselected from the group consisting of propoxylated bisphenol A,ethoxylated bisphenol-A, tetrabromo bisphenol dipropoxy ether, andmixtures thereof.
 16. The polymer according to claim 14, wherein thefirst monomer is 1,2-propane diol, the second monomer is diethylfumarate, the third monomer is dimethyl terephthalate and the fourthmonomer is propoxylated bisphenol A.
 17. The polymer according to claim14, wherein the first monomer is 1,2-propane diol, the second monomer isdimethyl fumarate, the third monomer is dimethyl terephthalate and thefourth monomer is 1,3-butane diol.
 18. The polymer according to claim14, wherein the first monomer is 1,2-ethane diol, the second monomer isdimethyl fumarate, the third monomer is dimethyl terephthalate and thefourth monomer is 1,2-propane diol.
 19. An unsaturated, linear polymercomprising:a reaction product of monomer comprising a low molecularweight diol having a molecular weight below about 200 and at least twodifferent monomers selected from the group consisting of carboxylicdiacids and diesters, said polymer having a glass transition temperatureranging from about 52° C. to about 61° C.
 20. A polymer according toclaim 19, wherein said monomers further comprise an aromatic dioldifferent from said low molecular weight diol.
 21. A polymer accordingto claim 19, wherein said monomers comprise 1,2-propane diol, dialkylfumarate and dialkyl terephthalate.
 22. A polymer according to claim 21,wherein said monomers further comprise propoxylated bisphenol A.
 23. Aprocess for preparing unsaturated linear polymer comprising a reactionproduct comprising first residues of a first monomer, second residues ofa second monomer and third residues of a third monomer, comprising thestep of:polymerizing a first monomer, having a molecular weight lessthan 200, a second monomer selected from the group consisting of anunsaturated dicarboxylic acids, diesters and anhydrides thereof, and athird monomer selected from the group consisting of aromaticdicarboxylic acids and diesters thereof, for a reaction time and at areaction temperature to form the unsaturated linear polymer.
 24. Theprocess according to claim 23, wherein the reaction product furthercomprises fourth residues of a fourth monomer.
 25. The process accordingto claim 23, wherein the polymerizing occurs under a vacuum to removereaction by-products.
 26. The process according to claim 23, wherein thereaction temperature ranges from about 150° C. to about 250° C.
 27. Theprocess according to claim 23, wherein the reaction time ranges fromabout 1 hour to about 5 hours.
 28. The process according to claim 23,further comprising, adding a catalyst to promote transesterification.29. The process according to claim 28, wherein the catalyst is selectedfrom the group consisting of tetraisopropyl orthotitanate, tetrabutylorthotitanate, monobutyl tin oxide and dibutyl tin oxide.